Here are a few images of the lead arm bend graph that I'll share with students. They show the common pattern and timing of the lead arm bending and straightening. The first one is an amateur, showing the arm bending through impact. The last three are pros, Grant Waite, Ernie Els, Steve Elkington showing the arm straightening. Els keeps his arm the straightest of anyone I've seen, but even it has a little bend to straight pattern.